Reliable, single event upset (SEU) tolerant systems are important to many applications. In particular, space borne applications having high speed communication rates frequently experience single event upsets in a high radiation environment. Additionally, many space borne applications having high speed communications need synchronization with ground equipment. Some applications needing synchronization with ground equipment include direct-sequence spread spectrum systems, frequency hopping systems, and synchronous stream encryption systems. A significant problem with some space borne applications needing synchronization with ground equipment occurs when a system element, such as a pseudo-noise generator, experiences an single event upset due to radiation.
Problems with maintaining synchronization between space borne applications and ground equipment typically increase as communication rates increase. Fast switching semiconductor technologies such as gallium arsenide (GaAs) and emitter coupled logic (ECL) are commonly used in high speed systems. In many space environments, elements fabricated using GaAs and ECL are highly susceptible to a radiation induced SEU. A problem with experiencing an SEU in a non-voting system is loss of synchronization between a transmitter and a receiver. Current systems typically counteract a loss of synchronization between transmitter and receiver by having the receiver alert the transmitter of the problem. During a loss of synchronization, an irretrievable data loss occurs. While voting systems have been used to solve a problem of lost synchronization, voting systems are susceptible to hard (e.g., hardware) failures.
Another problem with applications experiencing an SEU is security. For example, in data encryption applications, cautionary measures are commonly taken to avoid an inadvertent escape of sensitive data. Cautionary measures include automatic shut-off of output data when any processing discrepancy is detected. Such cautionary measures are a problem with a goal of uninterrupted communications between a transmitter and a receiver.
Thus, what is needed are a system and method tolerant to an SEU. What is also needed are a system and method capable of maintaining synchronization between a transmitter and a receiver after experiencing an SEU. What is also needed are a system and method which maintain continuous communications between a transmitter and a receiver following an SEU. What is also needed is a voter system which is tolerant of hard failures.